In what way is foreshadowing employed within the narrator's memory of his last conversation with Dr. Tokai?

During a conversation that the narrator describes as their last, Dr. Tokai and the narrator discuss Dr. Tokai's feelings of anger that well up when he thinks about possibly losing the woman he loves to another man or when he wants to see her but cannot. The narrator says that looking back, he should have replied to Dr. Tokai's concern with more helpful advice. In this moment, the reader is alerted to the fact that Dr. Tokai had been thrust into danger of some sort after his conversation with the narrator.